The science of emulsions and the techniques of emulsification are replete with analyses and theories representing continuing efforts to determine the true nature of oil-in-water emulsions (O/W) and water-in-oil emulsions (W/O). The true nature of emulsions involves, inter alia, (i) surface chemistry, e.g., the interfacial tension between the so-called disperse and the continuous phases, (ii) the physical properties of emulsions, including emulsion stability and the tendency to demulsify, to invert, to cream, (iii) the sensitive and very critical function of emulsifying agents, (iv) and the like.
Any number of equations and tables have been derived over the years as researchers persevere in their attempts, for example, to relate the viscosity of an emulsion to the viscosity of its continuous phase, and/or to the concentration of its internal phase, and/or to the interfacial film provided by emulsifying agents, and/or to the type of emulsifier and concentration thereof. Of course, the recondite principles inherent in electrophoretic studies of emulsions dramatically illustrate the quest for insight into the enigmatic entity known as an emulsion.
A well-respected emulsion textbook author, Paul Becher, expresses it better when he admits:
" . . . emulsion theory has progressed to a point where some sort of theoretical interpretation of emulsion behavior is possible; the prediction of emulsion behavior is still largely a matter of art rather than science." (Emphasis added) .sup.1/ FNT 1/ Becher, "Emulsions: Theory and Practice," (1957), page 85, American Chemical Society Monograph Series. Reinhold Publishing Corporation, N.Y. PA1 U.s. pat. Nos. 2,109,842 issued Mar. 1, 1938; 2,114,490 issued Apr. 19, 1938; 2,177,983 issued Oct. 31, 1939; 2,294,233 issued Aug. 25, 1942. PA1 "Emulsions of the water-in-oil type generally are not as stable as emulsions having water as the continuous phase. One reason is that the viscosity of the external phase changes with temperature." Page 1, col. 2. PA1 "When 5 percent of aluminum stearate is stirred into mineral oil, the powder partially dissolves at room temperature, and on heating the solution becomes clear. At around 100.degree. C the solution becomes highly viscous, behaving like a dispersion of a water-soluble gum in water. On cooling, the solution sets to a gel which is not very stable. Aluminum stearate is useful in W/O emulsions not only for its emulsifying activity but because it thickens or gels the oil phase. The high viscosity of the external phase helps to prevent coalescence of the water droplets and creaming of the emulsion." (Emphasis added) See paragraph bridging page 1, column 1 and page 2, column 1 of the periodical.
Typically, while Becher reports that early on it was found that the emulsifying agents " . . . sodium, potassium and lithium soaps . . . give O/W emulsions . . . [and] magnesium, strontium, barium, iron and aluminum soaps give W/O emulsions . . . ,".sup.2/ he is quick to qualify predictability throughout his text when reporting on research findings using mixtures of emulsifying agents, varied concentrations of emulsifying agents, varied internal phase ratios, and the like. FNT 2/ Ibid., page 86; ibid, cf. also page 88.
Another illustration in this vein is the author's discourse on the hydrophilic/lipophilic (polar/non-polar) characteristics of molecules. A linear C.sub.12 hydrocarbon, for example, terminated at one end with a polar (water-soluble) moiety, such as a carboxy group or its lower alkyl ester, is said to be amphiphilic, i.e., one end of the hydrocarbon is soluble in water and the other end is more soluble in non-polar organic solvents, such as benzene. From these observed characteristics there evolved over the years a method of selecting emulsifiers (surface active agents) on the basis of their so-called hydrophile/lipophile balance (HLB). Unfortunately, as Becher and others are quick to point out, experiences with emulsions reported throughout the literature reveal that the HLB method has by no means obviated the need for trial and error.
The following U.S. patents by Benjamin R. Harris, taken in conjunction with the Becher text, cited supra (footnote 1), give further insight (practical) into the hydrophile/lipophile properties of emulsifying agents used to form W/O emulsions:
The patents were uncovered in a recent study of the patent literature. In addition, the following patents were found:
______________________________________ Patentee/s Country U.S. Pat. No. Issued ______________________________________ Schanzle et al. U.S. 2,091,886 8-31-37 Muller U.S. 2,350,800 6-6-44 Nichols et al. U.S. 2,695,877 11-30-54 Telle et al. U.S. 3,127,311 3-31-64 Pader et al. U.S. 3,248,229 4-26-66 Lachampt et al. U.S. 3,846,546 11-5-74 Viout et al. U.S. 3,860,700 1-14-75 Meguro et al. U.S. 3,875,196 4-1-75 Lissant U.S. 3,892,881 7-1-75 Thomas U.S. 3,929,499 12-30-75 Johnson G.B. 417,715 10-1-34 ______________________________________
Broadly speaking, careful study of each of these references shows that they are readily distinguishable from the present claimed discovery and they neither implicitly or explicitly suggest same. This will become even more apparent from the more detailed description hereinbelow of the claimed invention.
The transition from emulsion art to emulsion science, so to speak, is an arduous experience; it records and portends a path strewn with shattered predictions. Witness the oldest emulsions, viz, cosmetic emulsions, the preparation of which has traditionally been an art. Success has been consequent on trial and error and the judgment and good fortune of the "cosmeticulous." Only fairly recently, according to Becher, supra, can " . . . broad generalizations . . . be made which will guide the uninitiated." (Emphasis added)..sup.3/ FNT 3/ Ibid., page 245
It will be shown, infra, that the present discovery advances the art in a way which inherently flies in the teeth of present-day scientific, albeit somewhat eclectic, rationale. Typical of findings leading to this rationale are those reported in the periodical "Norda Schimmel," No. 430, pages 1-3, April 1971, published by Norda/Schimmel International, New York, N.Y. in which it is pointed out that:
It is further noted that when calcium stearate or aluminum stearate is used as the emulsifying agent it is best formed in situ. See page 1, column 1, and page 2 columns 1 and 2.
According to the periodical, also, calcium stearate is insoluble in water and mineral oil, "but . . . sparingly soluble in mineral oil on heating." (Page 1, col. 1). Aluminum stearate, on the other hand, is "much more soluble in fatty oils and mineral oil" than calcium stearate: